Objective: A pilot study to examine the safety and efficacy of weight loss via intermittent fasting or continuous energy restriction in adults with type 1 diabetes and overweight or obesity. Research design and methods: Ten participants with type 1diabetes and overweight or obesity (8 women, 2 men) were randomised to either severe energy restriction (2510 kilojoules per day) on two 24-hour periods per week with 5 days per week of eating to appetite, or continuous moderate energy restriction (30% relative to weight maintenance energy needs) for 12 weeks. Participants were followed to 12 months. Results: There were no adverse events during the study, and rates of hypoglycaemia were unchanged. Body weight was reduced from baseline (P <0.05) by both intermittent fasting (−7.0%, range −5.2% to −8.0%) and continuous energy restriction (−3.9%, range −1.0% to −11.1%). Trunk fat was also reduced by these two interventions (P <0.05) (−12.2%, range −1.0% to −15.3% and −10.1%, range 2.3% to −10.7%, respectively). Blood pressure and circulating concentrations of HbA1c and lipids remained unchanged from baseline. There were no between group differences in these outcomes. Conclusion: These findings suggest that both intermittent fasting or continuous energy restriction are safe and effective weight loss approaches for people with type 1 diabetes and overweight or obesity.